NEW YORK ( TheStreet) -- Before you buy a stock, ask yourself if the company's products can easily be duplicated. If the answer is yes, then think twice, Jim Cramer said on "Mad Money" Tuesday. Today's markets are all about commodities versus proprietary products, and those companies that are commodities are getting tossed aside, he said.

Some companies can turn commodities into something proprietary, said Cramer, which is exactly how Starbucks ( SBUX) can charge twice as much for a cup of joe and why its stores command twice the same-store sales as rival Dunkin Brands ( DNKN). That's also why shares of DuPont ( DD) vaulted over 10% in today's trading, after management just hinted it may be leaving the commodity business that is titanium dioxide.

Things like fertilizer are true commodities, Cramer explained, but for things like paper, International Paper ( IP) has been able to transcend the market by expanding into emerging markets. The airlines have made the jump as well, thanks to a string of mergers and bankruptcies. But in technology, companies such as Seagate ( STX) and SanDisk ( SNDK) struggle to differentiate themselves.

Retail brands such as PVH Corp ( PVH) are unique, said Cramer, so they can command great margins. So, too, can orphan drug makers. But carbonated beverages? Not a chance. That's why those stocks are also under a lot of pressure of late.

Off the Charts

In the "Off The Charts" segment, Cramer went head to head with colleague Carly Garner over the direction of crude oil, which after a big spike in June and July has fallen sharply from $108 to $103 a barrel in just the past few days.

According to Garner's research, the price of West Texas Intermediary, or WTI, crude had a huge rally in June and July, fueled initially by worries over the Middle East, but later on by pure speculation. She noted the commitment of traders report, which measures the positions held by large and small speculators as well as those hedging their positions, shows a record level of long positions being held by speculators. The last time these traders made such a bullish bet was May 2011, and they lost big as oil declined sharply by $20 a barrel and kept on falling from there.

Garner also looked at the recent options action in the September $109 calls, noting that on July 19, these options sold for $2.30 but just five days later they plummeted to just 50 cents. The options traders have already left he building, she concluded, and the speculators won't be far behind.

Finally, looking at the weekly chart of crude, Garner noted a long-term ceiling of resistance that's held for over two years. She felt that crude would be unlikely to break that ceiling now, however the floor of support at just $90 a barrel seems far more likely as the relative strength indicator, or RSI, shows an extreme over-bought condition.

Cramer said he agreed with Garner's analysis and felt that the speculators have run wild with the price of crude, and will be reined in very soon.

Stepping Into Your Portfolio

Not all stocks should be judged by the same metrics, Cramer told viewers as he compared footwear giants Nike ( NKE) and Under Armour ( UA) to see which one deserves a spot in your portfolio.

Cramer said the choice between these two venerable names isn't always clear as Nike is the bigger, slower-growing colossus while Under Armour is the smaller, faster-growing underdog. Under Armour beat estimates by 2 cents a share when it last reported, increasing revenue by 23% and increasing margins. That news sent shares up a quick 12%. Meanwhile, Nike's earnings were only a modest upside surprise, which did little to move its shares.

In the area of innovation, Under Armour is innovating like crazy, while Nike management said it needed to "accelerate its innovation agenda." Nike trades at 18 times earnings with an 11% growth rate, while Under Armour trades higher, at 37 times earnings, but offers a 21% growth rate.

So which one is the winner? Cramer said in this case it's both. He said older investors would do well by investing in the more stable Nike, but younger investors could likely stomach the volatility in Under Armour and come out a big winner over the longer term. This is one case, Cramer concluded, where the right stock depends on the investor.

Executive Decision: Paul Hooper

In the "Executive Decision" segment, Cramer spoke with Paul Hooper, CEO of newly minted Gigamon Technology ( GIMO), the enterprise network equipment provider which just delivered a four-cents-a-share earnings beat on a huge spike in revenue.

Hooper highlighted two recent customers for Gigamon: the U.S. Supreme Court and the Library of Congress. He said the Supreme Court manages huge volumes of information on its network and Gigamon is helping to manage the infrastructure needed to move that information where it needs to go. Gigamon helps the court monitor network performance and properly scale the capacity of their network.

Meanwhile, at the Library of Congress, Hooper said that Gigamon's management tools offer broader visibility into what's happening on their network and also offers monitoring, management and security tools to help keep things flowing properly.

When asked about rivals like Cisco ( CSCO), Hooper said that Gigamon is vendor-agnostic, which means its customers can choose the best solutions for their needs rather than products from just a single vendor. Cisco, it turns out, is a partner, not a rival.

Cramer said that he's a fan of this recent IPO and would be a buyer on any weakness.

No Huddle Offense

Cramer said his rule for the show has been to never recommend a stock that trades with a price earnings ratio more than twice its growth rate. He said this rule has served him well over the years, helping to fend off some spectacular losses, albeit at the expense of some notable gainers.

Cramer said these three stocks are rule benders, stocks that are being propelled as if by an invisible force that gives them valuations that simply cannot be justified by "normal" metrics.

Sure, Amazon continues its domination of commerce while Netflix continues to grow like a weed and Tesla captures the imagination of drivers everywhere. But does that make these stocks great investments? Maybe, admitted Cramer, but certainly not for the faint of heart and not for "Mad Money" viewers.

At the time of publication, Cramer's Action Alerts PLUS had a position in CSCO and DD.

Jim Cramer, host of the CNBC television program "Mad Money," is a Markets Commentator for TheStreet.com, Inc., and CNBC, and a director and co-founder of TheStreet.com. All opinions expressed by Mr. Cramer on "Mad Money" are his own and do not reflect the opinions of TheStreet.com or its affiliates, or CNBC, NBC Universal or their parent company or affiliates. Mr. Cramer's opinions are based upon information he considers to be reliable, but neither TheStreet.com, nor CNBC, nor either of their affiliates and/or subsidiaries warrant its completeness or accuracy, and it should not be relied upon as such. Mr. Cramer's statements are based on his opinions at the time statements are made, and are subject to change without notice. No part of Mr. Cramer's compensation from CNBC or TheStreet.com is related to the specific opinions expressed by him on "Mad Money."

None of the information contained in "Mad Money" constitutes a recommendation by Mr. Cramer, TheStreet.com or CNBC that any particular security, portfolio of securities, transaction, or investment strategy is suitable for any specific person. You must make your own independent decisions regarding any security, portfolio of securities, transaction, or investment strategy mentioned on the program. Mr. Cramer's past results are not necessarily indicative of future performance. Neither Mr. Cramer, nor TheStreet.com, nor CNBC guarantees any specific outcome or profit, and you should be aware of the real risk of loss in following any strategy or investments discussed on the program. The strategy or investments discussed may fluctuate in price or value and you may get back less than you invested. Before acting on any information contained in the program, you should consider whether it is suitable for your particular circumstances and strongly consider seeking advice from your own financial or investment adviser.

Some of the stocks mentioned by Mr. Cramer on "Mad Money" are held in Mr. Cramer's Action Alerts PLUS Portfolio. When that is the case, appropriate disclosure is made on the program and in the "Mad Money" recap available on TheStreet.com. The Action Alerts PLUS Portfolio contains all of Mr. Cramer's personal investments in publicly-traded equity securities only, and does not include any mutual fund holdings or other institutionally managed assets, private equity investments, or his holdings in TheStreet.com, Inc. Since March 2005, the Action Alerts PLUS Portfolio has been held by a Trust, the realized profits from which have been pledged to charity. Mr. Cramer retains full investment discretion with respect to all securities contained in the Trust. Mr. Cramer is subject to certain trading restrictions, and must hold all securities in the Action Alerts PLUS Portfolio for at least one month, and is not permitted to buy or sell any security he has spoken about on television or on his radio program for five days following the broadcast.

President Trump's move Thursday to cancel his meeting with North Korea leader Kim Jong Un sent the stock market into a "tizzy," according to TheStreet's founder and Action Alerts PLUS Portfolio Manager Jim Cramer.